Human interferons (IFNs) are functionally-related cytokines that modulate both innate and adaptive immune responses. They are categorized in two groups, largely on the basis of sequence homology, as Type I and II. Type I IFNs include six types (IFN-α, IFN-β, IFN-ω, IFN-κ, IFN-ε, and IFN-λ). IFN-α, β, ω, and κ act through an identical IFN receptor, IFNAR. IFN-λ associates with a distinct receptor, IFNLR. The receptor for IFN-ε is currently unknown. Type II IFN consists of a single type (IFN-γ) and associates with the receptor IFNGR. While Type I IFNs are strongly induced during viral infections, Type II IFN is induced primarily in response to immune and inflammatory stimuli, and thus IFN-γ is frequently referred to as “immune IFN”. The most studied of the numerous Type I IFNs include IFN-α, IFN-β, and IFN-ω. Of these, IFN-α is the most complex, includes at least fifteen distinct protein subtypes exhibiting upwards of 75% sequence homology. Diaz (1995) Semin. Virol. 6:143-149; Weissmann et al. (1986) Prog Nucl Acid Res Mol Biol 33:251; J Interferon Res (1993) 13:443-444; Roberts et al. (1998) J Interferon Cytokine Res 18:805-816. In addition to having structural similarity, the IFN-α genes and their products show functional similarities. For example, they are induced by dsRNA or virus, and can interact with the same receptor, the IFNα/β receptor IFNAR. Mogensen, et al. (1999) J. Interferons and other Regulatory Cytokines, John Wiley & Sons. IFNα also inhibits apoptosis, promotes the survival and differentiation of antigen-activated T helper cells and promotes the maturation of functionally efficient monocyte-derived dendritic cells.
Many types of cells produce IFNα when exposed to viruses and dsRNA. Specialized leukocytes (called interferon-α producing cells (“IPCs”) produce IFNα in response to a wider variety of stimuli, e.g., viruses, bacteria and protozoa. Several in vitro studies indicate that the various IFN-α subtypes are produced to different extents by distinct IFN-α-secreting cell lines or in a virus type-specific manner following infection of human peripheral blood mononuclear cells (PBMCs), and that these patterns are often associated with subtype-dependent differences in anti-proliferative, anti-viral, and anti-tumor activities. However, the physiological significance of the individual subtypes and their synergistic or antagonist activities with one another in vivo remains undefined.
IFN-α has been implicated as a mediator of the pathology seen in several autoimmune diseases. Moreover, it can cause autoimmune disease development in patients treated with IFN-α for cancer and viral infections. Increased expression of IFN-α has been observed in the disease-localized tissues of patients with insulin-dependent diabetes mellitus (IDDM or type I diabetes), psoriasis, Crohn's disease, and celiac disease. Over expression of IFN-α has been observed in patients with systemic lupus erythematosus (SLE), IDDM and AIDS. In the case of SLE, which is characterized by an abundance of both autoreactive B and T cells, IFN-α expression is observed in not only tissue lesions but circulating within the blood of afflicted individuals. Furthermore, the IFN-α serum levels tend to correlate with the clinical disease activity index. This is believed to stem from cyclical induction of normally quiescent monocytes into potent antigen-presenting dendritic cells (DCs) as triggered by upregulation of IFN-α production by plasmacytoid DCs (pDCs). Indeed, the present inventors have previously demonstrated via oligonucleotide microarray analysis that SLE can be distinguished by “signatures” of unregulated genes involved in granulopoiesis and IFN induction; these signatures revert to normal upon high-dose infusion of glucocorticoids (U.S. patent application Ser. No. 11/228,586, the content of which is incorporated by reference hereto).
Systemic lupus erythematosus (SLE) is a systemic autoimmune rheumatic disease that is particularly aggressive in children and characterized by flares of high morbidity. Autoimmune diseases such as SLE often act in self-perpetuating cycles of relapse and remission. These cycles are often defined by phases of treatment with generally therapeutic regimens administered to quench the SLE disease cycle. FDA-approved treatment options for SLE include corticosteroids, nonsteroidal immune suppressants, antimalarials, and nonsteroidal anti-inflammatory drugs. These drugs abrogate the integrity of all immune effector responses rather than acting upon those specific to the pathogenesis of SLE. SLE represents an unmet medical need since these treatments are only partially effective with moderate to severe side-effects including bone thinning, weight gain, acne, anemia, sterility, rashes diarrhea, hair loss, and nausea. Furthermore, no new therapeutics for SLE have been approved in 40 years.
SLE has recently been closely linked to unabated IFNα production. Shi et al. (1987) Br. J. Dermatol. 117(2):155-159. IFNα is present at elevated levels in SLE serum (Crow et al. (2004) Curr. Opin. Rheumatol. 16(5):541-547) and plasmacytoid DCs (pDCs), the primary source of IFNα, accumulate in SLE skin. Farkas et al. (2001) Am. J. Pathol. 159(1):237-243. Moreover, it has been observed that some patients treated with IFNα have developed lupus (Okanoue et al. (1996) J. Hepatol. 25(3):283-291; Tothova et al. (2002) Neoplasma 49(2):91-94; and Raanani et al. (2002) Acta Haematol. 107(3):133-144) and that lupus patients that present with IFNα antibodies have been shown to display a milder form of the disease. Von Wussow et al. (1988) Rheumatol. Int. 8(5):225-230. IFNα may act via the differentiation of monocytes into functional dendritic cells (DCs) which in turn mediates the etiopathogenesis of SLE. Pascual V. et al. (2003) Curr. Opin. Rheumatol. 15(5):548-556. A proposed approach for the treatment of SLE is neutralization of IFNα (see Banchereau et al., PCT/US02/00343, the contents of which is incorporated by reference).
Although monoclonal antibodies (MAbs) that can block human IFN-α bioactivity have been produced, none have been reported to date that can neutralize all fifteen known subtypes, and few can neutralize naturally-derived, IFN-α-containing leukocyte IFN. PBL Biomedical Laboratories offers ten mouse monoclonal antibodies that bind to multiple human IFNα gene subtypes (see the world wide web at interferonsource.com/relativespecificity.html). However, each of the PBL antibodies bind the IFNα protein subtype encoded by human IFNα gene subtype 1 (IFNα protein subtype D) and from up to one to twelve other IFNα subtypes. U.S. Patent Publ. No. 2003/0166228A1 discloses a monoclonal antibody (designated 9F3) that was derived from immunization of mice with leukocyte IFNα (which includes all of the IFNα protein subtypes). The 9F3 MAb binds and neutralizes the anti-viral activity of the proteins encoded by seven human IFNα gene subtypes 1, 2, 4, 5, 8, 10 and 21 (which encode IFNα protein subtypes D, A, 4, G, B2, C and F, respectively), without neutralizing the antiviral activity of human IFNβ. This publication does not disclose whether the 9F3 antibody binds and inactivates the other eight IFNα gene subtypes, nor whether it binds to one or both of IFNα protein subtypes 4a and 4b. The PCT publication suggests using the monoclonal antibodies to treat disorders associated with increased expression of IFNα's, in particular, autoimmune disorders such as insulin-dependent diabetes mellitus and SLE. However, it is not known whether the 9F3 antibody is able to sufficiently neutralize the biological activity of the IFNα protein subtypes found in SLE serum.
Because IFNα is a multi-functional mediator of the immune response and has beneficial antiviral activity, complete inhibition or significant down-regulation of all IFNα subtypes is not an optimal therapeutic approach. Thus, a need exists for agents that will selectively neutralize the IFNα subtypes associated with pathological conditions. This invention satisfies this need and provides related advantages as well.